Cooling towers are heat exchangers of a type widely used to emanate low grade heat to the atmosphere and are typically utilized in electricity generation, air conditioning installations and the like. In a mechanical draft cooling tower for the aforementioned applications, airflow is induced or forced via an air flow generator such as a driven impeller, driven fan or the like. Cooling towers may be wet or dry. Dry cooling towers can be either “direct dry,” in which steam is directly condensed by air passing over a heat exchange medium containing the steam or an “indirect dry” type cooling towers, in which the steam first passes through a surface condenser cooled by a fluid and this warmed fluid is sent to a cooling tower heat exchanger where the fluid remains isolated from the air, similar to an automobile radiator. Dry cooling has the advantage of no evaporative water losses. Both types of dry cooling towers dissipate heat by conduction and convection and both types are presently in use. Wet cooling towers provide direct air contact to a fluid being cooled. Wet cooling towers benefit from the latent heat of vaporization which provides for very efficient heat transfer but at the expense of evaporating a small percentage of the circulating fluid.
In order to accomplish the required cooling, large industrial sized induced draft water cooling towers of either the crossflow or counterflow variety employ velocity head recovery stacks or external fan stacks or cylinders which are mounted in circumscribing relationship to the powered fan(s) associated with the towers and extend upwardly therefrom. The purpose of such stacks or cylinders is twofold. First, such stacks serve to discharge and guide hot exhaust air to a position above the tower where it diffuses into the ambient atmosphere and is carried away from the cool air inlet of the tower by the prevailing winds for example. It is necessary to discharge hot discharge air at an elevation where recirculation of such air back through the cool air inlets of the tower is prevented, since recirculation measurably lowers cooling efficiency. Second, stacks lessen fan horsepower requirements by virtue of “recovery” of pressure of air discharged therethrough, such occurring because of the diverging contour of the stacks.
Such external fan stacks are generally configured with a venturi-like restriction intermediate the ends thereof that surround the fan blade. They typically have a divergent upper discharge section above the fan blade in which reduction in air velocity and partial recovery of pressure occurs. As noted, such a stack configuration serves to lessen fan power requirements, and in large towers the savings can be significant.
The aforementioned fan stacks have drawbacks however. Said stacks are subject to the environmental elements such as high wind shear or wind load due to hurricanes for example, and thus can oftentimes require some sort of reinforcement or bracing to reduce the likelihood of fan cylinder and mechanical equipment damage. Current reinforcement or bracing systems utilized in the art have drawbacks as they can rupture the tower fan deck and/or fan stack at the respective attachment points in high wind conditions, causing more damage to the tower.
Accordingly, it is desirable to provide a cooling tower external stack support or bracing system that offers the requisite support during extreme environmental conditions while minimizing the risk of further damaging the cooling tower structure. The present invention addresses this desire.